iplink: add support for afstats subcommand

Add support for new afstats subcommand. This uses the new
IFLA_STATS_AF_SPEC attribute of RTM_GETSTATS messages to show
per-device, AF-specific stats. At the moment the kernel only supports
MPLS AF stats, so that is all that's implemented here.

The print_num function is exposed from ipaddress.c to be used for
printing the new stats so that the human-readable option, if set, can
be respected.

Example of use:

    $ ./ip/ip -f mpls link afstats dev eth1
    3: eth1
        mpls:
            RX: bytes  packets  errors  dropped  noroute
            9016       98       0       0        0
            TX: bytes  packets  errors  dropped
            7232       113      0       0

Signed-off-by: Robert Shearman <rshearma@brocade.com>
4 files changed